Synchronization system and method for audiovisual programmes associated devices and methods

ABSTRACT

The present invention relates in particular to a synchronization system and method. The synchronization system comprises a specification unit for specifying synchronization signals associated with an audiovisual programme, the latter comprising an audiovisual content and control information, a recognition unit for recognizing the synchronization signals in a transmitted stream carrying this programme, by recognition of at least one extracted portion of the audiovisual content, and an activation unit triggering an action in case of detection of these signals. The specification unit prepares and transmits to the recognition unit recognition elements making it possible to obtain this extracted portion, as well as at least one action timeout lag in case of detection of the synchronization signals. The recognition or activation unit then delays the triggering of this action according to the lag transmitted, in case of detection of the synchronization signals. In variants, the timeout lag is determined and/or the recognition elements are obtained independently of the specification unit.

The present invention concerns a synchronization system and method foraudiovisual programmes, as well as associated devices and methods. Itpertains in particular to units and methods for recognizing andspecifying synchronization signals.

Interactive television allows a viewer to act on the course of thetransmissions that he is watching. He can thus interact with interactiveservices. To do this, mass-market interactive terminals are connected toa dual communication network:

a bidirectional network (modem return path, cable, . . . ) ofpoint-to-point type, such as in particular a telephone network,implementing one or more point-to-point servers,

and a unidirectional distribution network, such as in particular an RF,cable or satellite TV broadcasting network, implementing one or moregeneral broadcasting servers; the expression “general broadcasting” (orjust broadcasting), is understood to mean the transmitting of identicaldata to a set of destinations, whether this be performed in particularby radio broadcasting, by cable or by Internet.

The relevant terminals consist for example of television receivers, DVB(standing for Digital Video Broadcasting) decoders or Internet decoders.The interactive services are generally downloaded into the terminals bybroadcasting via the unidirectional network. In other cases, they arehosted by servers that can be accessed by the telephone network. Theseservices are then accessed through references or web addresses (alsocalled URLs standing for Universal Resource Locators, or universaladdresses) broadcast as an adjunct to an audiovisual programme. Theydetermine the server to which the terminals must address themselves andthe service to be invoked on this server. The audiovisual programmesbroadcast synchronously either with the services, or with URLs of theservices, are then referred to as “enhanced programmes”.

In practice, the known techniques of interactive television rely on theoperations which follow. A broadcasting centre, or broadcaster,broadcasts an interactive service emanating from a services operator, ina manner synchronized with an audiovisual programme (unidirectionalnetwork). For this purpose, data relating to this service are embeddedwith audiovisual signals specific to this programme. When an interactiveterminal receives the enhanced programme thus obtained, it broadcasts onthe screen (image and sound) the audiovisual programme and interpretsthe data of the interactive service. It then screens the latter insynchronization with the audiovisual programme, typically in the form ofa video overlayed graphical or textual display.

A viewer can then interact with the interactive service, thisinteraction possibly leading to the setting up of a connection with aserver of the services operator (bidirectional network).

One of the essential aspects of interactive television relates to theestablishing and managing of synchronization between programmes andinteractive services data. In particular, it is generally envisaged tobroadcast the interactive content or its URL in a loop (carousel) forthe duration of the associated audiovisual programme. Two items ofbroadcaster equipment are customarily used for synchronization:

a traffic system, that creates an events execution list (playlist)comprising time information (start time and end time), objectinformation (device to be driven) and operation information (command tobe executed);

and an automaton system that manages the execution list so as to driveand control the broadcaster's broadcasting equipment (video servers,video recorders, subtitling apparatus, etc.).

The traffic system enables modifications to be made to the executionlist in case of significant modifications in the temporal organizationof the programmes. The automation system is for its part capable oftweaking the list in case of last minute tiny modifications, and ofredirecting the list to the traffic system if more consequentialmodifications are required.

The synchronizing of the interactive services with the programmes isachieved by incorporating a broadcasting server (which acts as server ofinteractive applications) from among the devices to be driven by theautomation system. The service operator is assumed to be connectedpermanently to the broadcaster's broadcasting server, so as to benotified of the actual broadcasting of the programmed contents. Thisinvolves a link of the TCP-IP (standing for Transmission ControlProtocol/Internetwork Protocol) type or the like in which a layer of aparticular application package can be deployed. This link serves in onesense to programme the broadcasting server on the basis ofadministration applications present at the service operator, and in theother sense to inform the services operator in particular of the stateof the broadcasting server, of the progress of broadcasts of contentsand of any incidents.

Problems of desynchronization between the broadcasting of the programmesand those of associated interactive contents are thus avoided.Specifically, if an audiovisual programme is delayed or advanced, theexecution list is updated by the broadcaster. In this way, the devicesused—including the broadcasting server—trigger at the appropriatemoments.

However, such a technique requires the intervention of the broadcaster,who must modify his events execution lists to take account of eventsrelated to the broadcasting of interactive services. Moreover, itrequires a convention between the broadcaster and the services operator,so that they understand one another with regard to commands relating tothe broadcasting of such services.

Various procedures have also been proposed in which synchronizationsignals are inserted into the audiovisual programme itself. Thus,document WO-01/50764 describes a computer method for utilizing aninteractive digital television transmission, in which service signalscorresponding to “synchronization pulse” sequences, which bring aboutthe downloading of a multimedia application, are detected. In U.S. Pat.No. 5,818,440, an interactive application is downloaded into aninteractive television network, and this application is automaticallyswitched on upon the detection of an application token incorporated intothe video programme.

Such implementations likewise require the intervention of a broadcasteror of a services provider in order to insert the stream of appropriatesynchronization signals, and therefore have an intrusive nature.

These difficulties are resolved by the invention disclosed in documentWO-01/91462. This priority document describes a device for synchronizingbroadcast audiovisual programmes and complementary information. Thedevice comprises a pictures and/or sound detection assembly capable ofextracting at least one semantic element from the content of anaudiovisual programme being broadcast. It also comprises a unit forrecognizing these semantic elements, linked to a programme guide whichcomprises a chronologically ordered list of information sets associatedwith the audiovisual programmes. The recognition unit, prepared by priorlearning, selects the information set which is most probably correlatedwith these semantic elements. A synthesis block then synchronizes theaudiovisual programmes with the information sets selected.

However, this invention demands complex means and requires reference toa programme guide.

Patent Application WO-02/21840 proposes a procedure for synchronizing aclient with a media signal. According to one embodiment of thisprocedure, one or more actions corresponding to an audiovisual signal(the media signal) is or are received, an application for performing theactions (for example by syntactic analysis—or “parsing”—of actioninformation) is determined, and a switching on of the actions istriggered by this application. In the examples described, an operatordefines actions that he dispatches to a server, which itself transmitsthem by broadcasting via the Internet to clients. Either the actionsdispatched have to be executed as soon as they are received, or they areaccompanied by time information making it possible to determine themoments at which to execute them.

A drawback of this procedure is that it demands relatively complexoperations in respect of synchronization, either in the form ofinterventions by an operator at suitable moments, or in the form ofprior preparation making it possible to trigger the dispatchings of theactions at the suitable moments.

Document WO-01/82623 discloses the automatic insertion of interactive TVtriggering messages (“triggers”) into an audiovisual data stream. Theinsertion can in particular be based on the recognition of particularelements in the stream, such as audio/video samples. Moreover, thisinsertion can be triggered before or after broadcasting of the stream.The description also mentions the use of a tag table comprising linksbetween, on the one hand, the samples to be found and, on the otherhand, interactive elements and associated attributes, such as, forexample, the station number.

This very flexible technology is, however, restricted to programmesknown in advance, for which the particular elements required must berecorded beforehand for the implementation of the recognitionoperations. In particular, it is not applicable to transmissionsbroadcast live.

One possibility for widening the field of applications of this type oftechnology would consist in introducing recognition elements intoaudiovisual programmes, these elements being able to trigger therecognition operations at the desired moments. For example, a specificbanner could be inserted during the broadcasting of a live transmission.However, such a solution would require inlay steps, that would have tobe performed by the transmitting station. This is therefore an intrusiveprocedure, which is rather impractical in particular when theinteractivity is driven by an operator who is not involved in thebroadcasting process.

The present invention relates to a system and a method of synchronizingaudiovisual programmes and interactive services, which may make itpossible to be completely unintrusive with regard to broadcasters andoperators of services, while permitting simple and reliableimplementation and avoiding recourse to a programme guide. The systemand the method of the invention enable applications not only toprogrammes known in advance, but also to transmissions broadcast live orto programmes that have not formed the subject of a processing or of aprior examination.

The synchronization system and method of the invention apply also toother types of synchronization relating to audiovisual programmes, inparticular in respect of automatic recordings of films or transmissions,or of automatic substitutions of contents of audiovisual programmes (theuser being able, for example, to decide in advance a real-timereplacement on screen of a certain category of programmes by another, bymeans of selection from among several broadcasting sources). What ismore, they also relate to radio transmissions. Hereinafter, and forsimplicity, including in the definition of the invention, the expression“audiovisual programme” is aimed at audio and/or video programmes.

The subject of the invention are also units and methods for specifyingand recognizing synchronization signals, usable for the

Document WO-01/60061 deals with methods and apparatus for recordingprograms prior to or beyond a preset recording time period. Inaccordance with the described technique, a video signal is processed togenerate one or more signatures associated with a broadcast program tobe recorded. The signatures are then further processed, for example bybeing compared with known stored information regarding the broadcastprogram, so as to determine an actual start time and end time of theprogram.

The teaching of that document seems interesting in that it introducessome flexibility in the recognition of the exploited synchronizationsignals. It mentions notably solutions in which recognition is possibleeven when no specific synchronisation signals are introduced inbroadcast signals and when no reference signal is previously stored atthe receiving side. This is possible by exploiting the detection ofrelevant variations in the received audio and/or video signals. However,the signatures may not be always easy and practical to process, becausesignificant detectable signals or signals variations are not necessarilyavailable without being specifically introduced upstream, every time asynchronisation is needed. synchronization system of the invention andcapable of offering the aforesaid advantages.

It is also aimed at a broadcasting centre (broadcaster), a serviceoperator, a terminal (interactive or otherwise) for receivingaudiovisual programmes and software, which are associated with one atleast of the abovementioned subjects of the invention.

For this purpose, the subject of the invention is a recognition unit forrecognizing synchronization signals in at least one audiovisualprogramme received, that audiovisual programme comprising an audiovisualcontent intended to be broadcast to users (that is to say which isrealized in visual or audible form) and control information. Therecognition unit is in accordance with claim 1.

The recognition unit of the invention is therefore capable of detectingsynchronization signals without any modification being made to theaudiovisual programmes, by direct analysis of the audiovisual content(such as pictures, sounds, parts of the latter or combinations)broadcast to the users. Thus, by contrast with the intrusive methodsconsisting in intervening on the event playlists, no modification ofthese lists is necessary. In particular, in this way the risks ofbroadcasting an interactive service on an audiovisual programme thatdoes not correspond are reduced. Specifically, by virtue of therecognition pertaining to the content, an error has a small possibilityof occurring, while with the above methods, these risks are considerablyincreased through the manipulating of identification entities and thepresence of a third party providing information which cannot be verifiedby the services operator (identifier of the programme).

Moreover, in contradistinction to the techniques relying on therecognition of specific detection signals incorporated into theaudiovisual programme streams transmitted, no action on the signalscarrying these programmes is required.

What is more, as compared with the technique disclosed in PatentApplication WO 01/91462, the recognition elements are communicatedbeforehand to the recognition unit, thereby making it possible to avoidrecourse to complex identification techniques associated with aprogramme guide.

Moreover, the recognition unit of the invention contrasts with theteaching of the prior document WO 01/82623 through the presence of thetimeout module, which introduces a lag before the transmission of theaction instructions when the synchronization signals are detected in theaudiovisual programme. The use of this lag is particularly beneficial,in so far as it makes it possible to lock the synchronization withrespect to an event that can be anticipated, then to meter the time gapbetween this synchronization and a suitable moment, so as to trigger atthis moment the actions to be synchronized.

Thus, in particular, a live transmission generally being preceded—oreven punctuated—by adverts, it is possible to lock the detection onto anend of advertising banner credits and adjust the timeout so that aninteractive service is displayed, for example, 10 minutes after thecommencement of the transmission (by way of illustration, the timerequired by a promoter to announce the possibility of interacting withhis television).

This technique may in particular allow a services operator to managesynchronization operations, including with regard to transmissionsbroadcast live, without having to ask a station broadcasting thetransmissions to take a demanding part in these operations. It is infact sufficient for the station to provide a sample, such as for examplean image of an advertising banner, and an approximate timing for thetriggering of desired actions, for example the appearance ofinteractivity. In particular, this embodiment allows synchronization ofthe broadcasting of interactive services with audiovisual programmesthat are designed a priori without any interactivity.

The recognition unit of the invention can also serve in particular totrigger in due course at the level of a terminal, local interactivity orrecording during the broadcasting of a film or of a transmission,without it being necessary for this terminal to be supplied beforehandwith extracted portions of their content. It is sufficient for theterminal to be capable of recognizing portions of a programme broadcastbeforehand (advertising, opening credits for a broadcast or a series,etc.). This recognition can then provide a reference time, on the basisof which several subsequent instants can be accurately determined bymeans of predefined timeouts. The invention can thus be particularlyadvantageous in the case where the synchronization is implemented at thelevel of receivers, since it can make it possible to reduce thedispatching and recording of reference events (gain in bandwidth, inprocessing time and in space required for storage).

The use of a lag, designed to delay the triggering of an action in caseof detection of the synchronization signals, appears to be particularlyunexpected having regard to the commonly accepted concepts.Specifically, the concept of lag is associated in the state of the artwith a bringing into action at a precise and predefined instant, thatthe lag makes it possible to specify (such as, for example, in the priordocument WO 02/21840, page 8, lines 17-24). On the contrary, in theinvention, the lag leads to a non-predefined and unforecastable instantthat is conditioned and made precise through the detection of thesynchronization signals.

In the definition of the recognition unit, as in the remainder of thepatent application, the “units” and “modules” are to be understood in afunctional sense, and are therefore not limited to particularrealizations. Thus, they may in particular be grouped together into oneand the same component or one and the same piece of software, or on thecontrary be dispersed among various components. Moreover, therecognition unit can be installed broadcasting side (typically at thebroadcaster's premises), service operator side, or in a terminal forreceiving audiovisual programmes, preferably an interactive one, inembedded form.

The recognition elements received and/or the portions extracted can beapplied to one or to several programmes, broadcasting simultaneously orsuccessively. For example, programmes being recurrent over time, it issufficient to transmit images just once for a synchronization toactually be programmed.

Moreover, to a given detection of synchronization elements, there maycorrespond several timeouts defining successive instants. The timeoutand transmission modules are then able to use a detection instant as areference instant, from which the timeout module determines severalinstants for triggering dispatching of action instructions. In asophisticated version, the timeout module is able to combine morecomplex information than a single detection instant and predefineddurations to determine these triggering instants. Such information mayin particular consist of:

several detection instants (for example two detection instants serve tospecify at least three instants for triggering dispatching ofinstructions);

operators pertaining to the synchronization signals detected (forexample, distinct extracted portions are associated respectively withvarious groups of lags);

detection time slots (for example the lags are shorter if the detectionsare performed during later time slots);

or any combination of the above information.

Preferably, the modules for receiving and recording the recognitionelements in the recognition unit are designed so as respectively toreceive and record also at least one timeout lag and the timeout moduleis designed to use this lag. According to other embodiments, the lag ispredefined, or determined locally by the user.

Advantageously, the modules for receiving and recording recognitionelements and the module for transmitting action instructions aredesigned so as respectively to receive, record and transmit identifiersrelating to the actions to be triggered. The recognition criteria andthe actions to be performed are thus specified at one and the same time.

In a preferred form of communication of action identifiers, recognitionelements and action identifiers are received jointly in the form ofpairs, each of these pairs comprising a set of recognition elements andan associated identifier of actions.

In other embodiments, the action identifiers are received separately andare applied to all the detections subsequently performed with thesuccessively transmitted recognition elements. In yet other embodiments,the actions to be triggered are predefined, or decided by usersindependently of the recognition operations.

Preferably, each of the portions of content consists of at least one ofthe following portions: an image, an image part, a sound and anycombination of at least two of these portions.

In a first advantageous form of the recognition elements, the latterinclude at least one boolean operator. The detection module is designedto detect at least two of the portions of content in conjunction withthis boolean operator (such as, in particular, “and” or “or”) and thetransmission module is designed to transmit the action instructions incase of such detection.

For example, identifications associated with action identifiers arecombined in the following manner:

if (image 1 detection AND image 2 detection), then trigger action 1,

if (image 3 detection OR image 4 detection), then trigger action 2.

In a second advantageous form of the recognition elements, the latterinclude at least one time information item. The detection module isdesigned to detect the portions of content in conjunction with this timeinformation item and the transmission module is designed to transmit theaction instructions in case of such detection. Preferably, this timeinformation item comprises at least one information item chosen fromamong a date of detection and a detection time slot.

For example, a start of detection date/time and an end of detectiondate/time are indicated for each detection, thereby making it possibleto restrict the number of comparisons to be performed for eachrecognition element received. This technique is beneficial in particularfor the broadcasting of interactive services. Specifically, the time ofbroadcasting of an audiovisual programme is generally known to within afew minutes and only one service is broadcast at a time, so that theprogramming of a single detection at a given instant is sufficient totrigger the broadcasting of this service.

In another example, the detection of the portions of contents iscombined with tests on the current date:

if (image 1 detection AND image 2 detection), then trigger service 1,

if (image 3 detection AND current_date( )==06092002), then triggerrecording.

In a third advantageous form of the recognition elements, the latterinclude at least one channel reference. The detection module is thendesigned to detect the portions of content in conjunction with thischannel reference and the transmission module is designed to transmitthe action instructions in the case of such detection.

By transmitting an information item regarding the station on whichdetection should be done, one avoids unnecessarily invoking therecognition unit when no detection is programmed on the current station.This extra information item also makes it possible to programmedetection on a station in particular, the recognition element to bedetected possibly being broadcast on several stations—for example acommercial break. By default and without any information as to station,the detection is preferably activated permanently and withoutdistinction of station.

Upstream of the recognition unit, the extracted portions of the contentof the audiovisual programme can be obtained directly and explicitlyfrom the programme, or be determined separately from the programme byvirtue of knowledge of the latter. For example, this may involve a wordor a group of words that a presenter has to utter, or an object that hasto appear on the screen. In all cases, the portion of content is known apriori, and communicated to the recognition unit prior to thetransmission of the audiovisual programmes. The recognition may thus beof a deterministic nature, and not be based in any way on statistical orexperimental matches (such as the teaching of document WO 01/91462).

On the other hand, in advantageous embodiments, the detection of thesynchronization signals relies on the recognition of several portions ofcontent, or on the crossing of recognition of such portions with othertypes of information (station, system variable such as the current date,possibly programme guide, etc.). Thus, several images are advantageouslyused in case of uncertainty regarding the content of the programme or inorder to boost the chances of detection of the programme, the detectionof one of the images triggering the action process.

Three preferred modes of obtaining the portions extracted by therecognition unit are distinguished, the latter advantageously combiningthe capabilities of at least two of these embodiments:

the recognition elements include the extracted portion; the extractedportions included in the recognition elements are thus advantageouslytransmitted to the recognition unit by a specific unit (such as thatdefined hereinafter as the “specification unit”);

the recognition elements comprise instructions for extracting theportion of content in at least one stream of an audiovisual programmepreviously received by the stream reception module; the recording moduleis then designed to extract directly this portion of the streamaccording to the extraction instructions and to record it in the storagespace;

and the recognition elements include at least one identifier of theextracted portion, this portion being intended to be recorded in thestorage space prior to a detection (as described above).

In the embodiment with extraction instructions, it is possible toreceive and record directly the portions extracted from the audiovisualprogrammes received, under the effect of instructions for extractions atdetermined instants and according to determined conditions. The modulefor receiving the transmitted stream is then utilized as part of therecognition elements reception module.

This avoids voluminous transmissions of information, that might be verypenalizing in certain cases (for example, communication of completeimages in an analogue television environment, for which the bandwidth interms of data is reduced to a few tens of k-bytes/second).

Thus, according to an advantageous embodiment with implementation of therecognition unit in a terminal, a trigger of particular type is used,indicating to the terminal the fact that the image or the soundbroadcast at the moment of receipt of the trigger must be stored, asmust the extracted-portion identifier transmitted with the trigger. Inpractice, the accuracy in the synchronization between the receipt ofthis trigger and the broadcasting of the image or of the sound to berecorded is not paramount, in so far as any extracted portion whatsoeverof a determined sequence able to serve as tag (for example broadcastingof advertising banner credits) may be suitable.

Moreover, in an embodiment combining the modes of obtainment byinclusion of portions in the recognition elements and by utilization ofidentifiers, the reception and recording modules are able to receive andstore extracted portions utilizable for several distinct types ofdetection. Each portion or set of portions associated with a type ofdetection is then specified by a one-to-one portion identifier. Thisprior storage allows the subsequent dispatching to the recognition unitof recognition partial elements including the identifiers of portionsinstead of the extracted portions themselves. These recognition partialelements, which may comprise recognition information such as inparticular time slot, broadcasting channel and/or boolean operator, arepossibly accompanied by action information and/or timeout information.Thus, the recognition elements in their entirety are obtained in atleast two successive steps: extracted portions, then associatedrecognition instructions.

This embodiment avoids bandwidth-hungry multiple operations oftransmitting one and the same extracted portion, once the initial stepof transmitting this portion has been accomplished. Moreover, even incase of single use of an extracted portion, it makes it possible toanticipate subsequent recognition instructions. Thus, the extractedportions can be dispatched in periods of greatest availability ofbandwidth (typically, at night or during the weekend) and subsequentlycommunicate the recognition instructions, which may require only a smallbandwidth (since the portion identifiers are sufficient to unambiguouslydesignate these portions). In this way, even if these instructions aretransmitted only shortly before they are implemented, the reliability oftheir reception and of their utilization in due course is substantiallyincreased.

The advantages mentioned hereinabove are particularly beneficial if therecognition unit is installed in a terminal, or more generallydownstream of an extended communication network designed to support thetransport of the extracted portions.

The invention also relates to a specification unit for specifyingsynchronization signals associated with at least one audiovisualprogramme, this (or these) audiovisual programme(s) comprising anaudiovisual content intended to be broadcast to users and controlinformation, and the synchronization signals being intended to bedetected in at least one transmitted stream carrying this audiovisualprogramme and to thus trigger at least one action.

According to the invention, the specification unit comprises:

a preparation module for preparing recognition elements making itpossible to obtain at least one extracted portion of the content of theaudiovisual programme,

and a transmission module for transmitting the recognition elementsindependently of transmissions of the audiovisual programme, to at leastone recognition unit intended to detect the synchronization signals inthe transmitted stream carrying the audiovisual programme, byrecognizing the extracted portion(s) in the content of the audiovisualprogramme.

The preparation and transmission modules of this specification unit aredesigned respectively to prepare and transmit at least one actiontimeout lag in case of detection of synchronization signals.

This specification unit is preferably capable of cooperating with anyone of the embodiments of the recognition unit of the invention. Theaction timeout lag transmitted by the specification unit can also beutilized downstream of the recognition system, at the level of theexecuting of the actions.

More precisely, in a first form of use of the timeout lag, the latter isdesigned to bring about a timeout between the detection of the detectionsignals and the transmission of action instructions. The lag is thenpreferably transmitted separately from the recognition elements andaction identifiers, and jointly with the corresponding elements andidentifiers. In a second form, it is designed to bring about a timeoutbetween the reception of action instructions and their triggering. Thelag is then preferably incorporated into a corresponding actionidentifier.

Preferably, the preparation and transmission modules of thisspecification unit are designed respectively to prepare and transmitidentifiers relating to the actions to be triggered in case of detectionof the synchronization signals.

The action identifiers then advantageously relate to at least one of thefollowing actions: broadcasting of an interactive service, triggering ofan interactive service, triggering of an update of an interactiveservice, triggering of a recording of the audiovisual programme andconnection to a website. The first action is more specifically intendedfor a detection of synchronization signals at the level of a broadcasteror of a services operator, while the last three actions are typicallyapplicable in the case where the recognition is performed in a terminalfor receiving audiovisual programmes (for example triggering of anembedded service, possibly consisting in the triggering of itsappearance).

It is thus possible to distinguish in particular two embodimentsimplementing an action timeout lag:

local determination of the lag at the level of the detecting of thesynchronization signals or of the executing of the action (predefinedlag or one chosen by a user);

or determination of the lag upstream of the detection, preferably at thelevel of the specifying of the recognition elements.

Moreover, in each of these two cases, it is possible to envisage anapplication of the action timeout lag at the detection level, or at theaction execution level.

Moreover, in other embodiments already alluded to above, thisdetermination can pertain to criteria giving the timeout lag or lags.For example, pairs of lags and of time slots respectively associated aredetermined for the detecting of the synchronization signals.

As far as the recognition elements are concerned, the following threeembodiments are distinguished for the obtainment of the extractedportion:

the recognition elements include this extracted portion;

the recognition elements comprise instructions for extracting thisextracted portion in at least one stream of an audiovisual programmepreviously received by the recognition unit;

and the recognition elements include at least one identifier of thisextracted portion previously recorded in the storage space.

The invention also relates to an assembly for activation by recognitionof synchronization signals in at least one audiovisual programmereceived, comprising a recognition unit and an activation unit and inaccordance with claim 15. In such an activation assembly, the triggeringdelay by means of the timeout lag is applied either by the recognitionunit, or by the activation unit, or by both (two aggregated delays). Itis beneficial for the recognition unit to be in accordance with one ofthe embodiments of the invention.

According to an advantageous form, the activation assembly is designedto receive said timeout lag with the recognition elements.

The invention applies also to a synchronization system as defined inclaim 17, comprising a unit for specifying synchronization signals, aunit for recognizing the synchronization signals, and an activation unitdesigned to trigger at least one action in case of detection of thesynchronization signals by the recognition unit.

The recognition unit, the specification unit and/or the activationassembly made up of the recognition and activation units, are preferablyin accordance with any one of the embodiments of the invention.

The subjects of the invention are also a broadcasting centre, a servicesoperator and a terminal for receiving audiovisual programmes, comprisinga specification module, a recognition module, an activation assemblyand/or a synchronization system which are in accordance with any one ofthe embodiments of the invention.

In the case where the recognition unit is in a reception terminal,according to an advantageous implementation, recognition elements andassociated interactive services are advantageously transmitted in phaseadvance to the terminal. When, for example, the viewers are offered nointeractivity, this makes it possible to increase the proportion oftelevisions capable of offering interactivity. The terminal thenpreferably has means for storing the recognition elements andinteractive services in the permanent memory, for example of flash type.This embodiment makes it possible to program continuing synchronizationswith switch offs and switch ons of the terminal. In this way, thechances of offering interactivity are increased despite a completeprovisional shutdown of the system.

In a first mode of dispatching the recognition elements and associatedservices to a terminal comprising a recognition unit, one or moreassociations of sets of recognition elements and of correspondinginteractive services are transmitted jointly (in phase advance),preferably by broadcasting. The dispatching of several associations ofthis type which are intended to be utilized in parallel is completed bycommunicating action identifiers coupled to the sets of elements, theseidentifiers indicating which services are the ones to be instigated.

In a second mode of dispatching the recognition elements and associatedservices to a terminal comprising a recognition unit, the dispatching ofthe recognition elements and of the services is separated. Actionidentifiers are then attached to the recognition elements so as to makethe latter correspond to the services to be instigated.

The invention also relates to a method of activation by recognition ofsynchronization signals in at least one audiovisual programme received,in accordance with claim 21. This recognition method is preferablyimplemented by means of an activation assembly in accordance with anyone of the forms of the invention.

The invention moreover relates to a method of specifying synchronizationsignals and a method of synchronization which are respectively inaccordance with claims 22 and 23. These methods are preferablyimplemented respectively by means of a specification unit and asynchronization system which are in accordance with any one of the formsof the invention.

Preferably, in the methods defined hereinabove, the audiovisualprogrammes comprise at least one recognition part containing at leastone of the recognition portions, and at least one live transmissionintended to be broadcast following the recognition part. In this way,the synchronization signals are detected during the broadcasting of therecognition part and the action is triggered during the broadcasting ofthe following live transmission, by means of the timeout lag.

The subject of the invention is also a computer programme product,characterized in that it comprises programme code instructions forexecuting the steps of one of the methods according to the inventionwhen this programme is executed on a computer. The expression “computerprogramme product” is understood to mean a computer programme supportthat can consist not only of a storage space containing the programme,such as a diskette or a cassette, but also of a signal, such as anelectrical or optical signal.

The invention will be better understood and illustrated by means of thefollowing wholly nonlimiting exemplary embodiments and implementations,with reference to the appended figures in which:

FIG. 1 is a basic diagram of a synchronization system in accordance withthe invention;

FIG. 2 represents a specification unit of the synchronization system ofFIG. 1;

FIG. 3 represents a recognition unit of the synchronization system ofFIG. 1;

FIG. 4 represents an activation unit of the synchronization system ofFIG. 1;

FIG. 5 diagrammatically illustrates a communication network comprising abroadcasting centre (or broadcaster) together with a broadcastingserver, a services operator together with point-to-point server and amass-market terminal, interactive or otherwise;

FIG. 6 shows the time profile of a carousel broadcast of services;

FIG. 7 shows a first mode of implementation of the synchronizationsystem of FIG. 1 in the communication network of FIG. 5, withsynchronization system at the services operator's premises;

FIG. 8 shows a second mode of implementation of the synchronizationsystem of FIG. 1 in the communication network of FIG. 5, withspecification unit at the services operator's premises and recognitionand activation units at the broadcaster's premises;

FIG. 9 shows a third mode of implementation of the synchronizationsystem of FIG. 1 in the communication network of FIG. 5, withspecification unit at the broadcaster's premises and recognition andactivation units in the terminal;

and FIG. 10 represents in diagrammatic form a set-up of the recognitionand activation units in the terminal, for the mode of implementation ofFIG. 9.

A synchronization system 5 (FIG. 1) is designed to synchronizeaudiovisual programmes 15 and interactive services S. It comprises asynchronization signals specification unit 1, able to prepare pairs 10each consisting of a set of recognition elements 11 and of an actionidentifier 12, from audiovisual programmes 15 and selection operationsperformed by a user, before broadcasting of the programmes 15 over anetwork. In each of these pairs 10, the recognition elements 11 includeat least one extracted portion of the content of the programme 15, whichportion is intended to serve as synchronization signal (at leastpartial). The action identifiers 12 of each of the pairs 10 containinformation relating to the execution of actions in case of detection ofsuch synchronization signals in the streams carrying the programmes 15.

A recognition unit 2 is designed to record the pairs 10 originating fromthe specification unit 1, to use them upon receipt of streams carryingthe programmes 15 so as to recognize the portions of content in theprogrammes and, under the conditions defined by the sets of recognitionelements 11, to identify occurrences of synchronization. It is alsointended to transmit the action identifiers 12 for triggering of theseactions, in case of detections of identification signals correspondingto these actions.

An activation unit 3 is designed to receive the action identifiers 12originating from the recognition unit 2 and to trigger the appropriateactions A.

The three units 1, 2 and 3 of the synchronization system will now bedetailed, with reference respectively to FIGS. 2, 3 and 4. Thespecification unit 1 (FIG. 2) comprises an input module 31 for theaudiovisual programmes 15 and a module 32 for controlled broadcasting toan operator of contents 16 of these programmes 15. The programmes 15, orat least significant parts of these programmes (picture, sound, colourof a banner, etc.), are for this purpose available in phase advance forthe operator responsible for programming the synchronization system 5.Typically, the latter has available a recording on cassette or DVD, or asequence intended to be inserted into a transmission. The operator can,for example, view one of the programmes 15 picture by picture, or listento certain passages of sound.

A user interface 33 of the specification unit 1 allows the operator toinput commands 17 in conjunction with this controlled broadcasting. Itpermits the operator to select pictures, sounds, parts of pictures orcombinations of these portions of content, so as to construct them intorecognition elements 11. The interface 33 also allows him to define morecomplex recognition criteria, based on conjunctions or alternatives(respectively: several portions, or at least one portion from several,to be recognized), time criteria (date, time slot) or stations. Theinterface 33 also allows the operator to define action identifiers 12associated with the recognition elements 11, such as the triggering orthe broadcasting of an identified interactive service, and timeout lags,between the detecting of synchronization signals and the triggering ofcorresponding actions. Such lags are:

either transmitted separately in the form of lags 13 designed for atimeout between a detection by the recognition unit 2 and a transmissionof the action identifiers 12 to the activation unit 3,

or incorporated into the action identifiers 12 for timeouts betweentheir reception by the activation unit 3 and the triggering of thecorresponding actions A.

The joint use of the two types of lags is also possible.

A preparation module 34 establishes the pairs 10 and the lags 13 as afunction of the operator's commands and communicates them to atransmission module 37 for transmission to the recognition unit 2. Thispreparation module 34 comprises in particular a submodule 35 forextracting the portions selected from the programmes 15 and a submodule36 for defining the action identifiers 12.

The recognition unit 2 (FIG. 3) comprises for its part a receptionmodule 21 for receiving the audiovisual programmes 15 and a receptionmodule 24 for receiving the information originating from thespecification unit 1, including the pairs 10 and the timeout lags 13. Arecording module 25 makes it possible to automatically record thisinformation in a storage space 20.

The recognition unit 2 also comprises a synchronization signalsdetection module 22 intended in particular for comparing the contents ofthe programmes 15 with the portions of contents of the recognitionelements 11, contained in the pairs 10 stored in the storage space 20.The detection module 22 is in conjunction with the information sourcescapable of serving for the identification of the selection criteria, forexample a clock 28 providing time information in case of time criteria(date, time span). The detection module 22 is designed to communicatethe action identifiers 12 and the associated timeout lags 13 as they arein case of detection of the synchronization signals, to a transmissionmodule 23 for transmitting instructions via a timeout module 26. Thefunction of the latter is to possibly time out the transmission in thepresence of timeout lags 13, while the transmission module 23 isintended to transmit the action identifiers 12 to the activation unit 3as they are.

In an improved version, the interface 33 and the preparation module 34of the specification unit 1 permits the operator not only to shape therecognition elements 11 including the portions of contents to be usedfor detection, but also to proceed in another manner, by formulatinginformation which allows the recognition unit 2 to identify and obtainthe portions of contents via the reception module 21 for receiving theaudiovisual programmes 15. For example, this information may consist ofa channel and a timetable, this timetable possibly being replaced by anindicator of instantaneous selection. This information may be dispatchedin the form of triggers, designed to trigger at the level of therecognition unit 2 the extraction and the recording of the targetedportions.

The recording module 25 of the recognition unit 2 is then capable ofproceeding to the recording of the extracted portions as a function ofthe information transmitted by the specification unit 1, without theseportions having had to travel between the specification unit 1 and therecognition unit 2.

The activation unit 3 (FIG. 4) comprises a reception module 41 forreceiving the action identifiers 12, a module for extracting actioninformation from these identifiers 12, and for transmitting actioninstructions 18 and timeout lags 19, if any, to an action triggeringmodule 44, via a timeout module 43. The function of the latter is totime out the transmission of the action instructions 18 as they are,according to the timeout lags 19. The job of the triggering module 44 isto trigger the actions A targeted by the action instructions 18, as soonas the latter are received.

The synchronization system 5 will now be set forth in several practicalapplications of interactive television, involving a communicationnetwork (FIG. 5) which comprises a broadcaster 50, a services operator60 and a mass-market interactive terminal 70. The broadcaster 50 islinked to terminals of the type of the terminal 70, by amono-directional network 81 (an RF cable or satellite TV broadcastingnetwork). The services operator 60 may or may not be linked to theterminal 70, by a bi-directional network 82 (modem return path, cable,etc.) of point-to-point type, such as the telephone network. Thebroadcaster 50 and the services operator 60 are, for example, connectedto one another by a link 83 of the TCP-IP type, on which a bus inaccordance with the CORBA (standing for Common Object Request BrokerArchitecture) standard is deployed.

It is envisaged that the broadcaster 50 broadcasts in a loop (carousel)interactive contents or their URLS, called interactive services S forsimplicity, for the duration of the associated audiovisual programmes15. In an operational example (FIG. 6), the broadcaster 50 broadcastssuccessively in the course of the time t the services S1, S2 and S3 in aloop, jointly with the respective enhanced programmes PG1, PG2 and PG3,until instants of end of availability FS1, FS2 and FS3 of the servicesS.

In a first embodiment (FIG. 7), the synchronization system 5 isinstalled in a computer 62 of the services operator 60 and is controlledby an operator 61 via a network 84. When operational, the following iscarried out:

Step 1: programming of the specification unit 1 of the synchronizationsystem 5, by locking onto the station where the audiovisual programme 15is broadcast and defining of pictures and/or sounds to be detected(recognition elements 11) and the action identifier 12 to be dispatched;

Step 2: when the moment of broadcasting the programme 15 has arrived, avideo server or a video recorder of the broadcaster 50 commences thebroadcasting of the audiovisual programme 15;

Step 3: broadcasting of the audiovisual programme 15 alone (viabroadcasting relays 56);

Step 4: the synchronization system 5 then receives the audiovisualprogramme 15 pictures with which it has to synchronize an interactiveservice S and analyses them;

Step 5: when the programmed picture is detected, the synchronizationsystem 5 notifies a broadcasting server of the broadcaster 50, which canthen trigger the broadcasting of the interactive service Ssimultaneously with the audiovisual programme 15;

Step 6: broadcasting of the interactive service S and of the audiovisualprogramme 15 simultaneously.

In a second embodiment (FIG. 8), the specification unit 1 is installedwithin the services operator 60, as in the first embodiment of FIG. 7,but the recognition 2 and activation 3 units are installed in thebroadcasting server of the broadcaster 50. The course of the operationalsteps is for the remainder similar to that of the first embodiment.

In a third embodiment (FIG. 9), the specification unit 1 is nowinstalled at the broadcaster 50, and the recognition 2 and activation 3units are embedded in the terminal 70. More precisely (FIG. 10), theterminal 70 comprises a block 71 for retrieving broadcast signals(involving the operating system and drivers), which is designed toreceive in particular pictures to be detected (more generally: pairs 10of sets of recognition elements 11 and of action identifiers 12) andinteractive services S. This block 71 is designed to communicate thepictures to be detected to the recognition unit 2, and the interactiveservices S to an interactivity or presentation engine 72.

While operational, the following is carried out:

Step 1: programming by an operator of the broadcaster 50 of therecognition unit 2 of the synchronization system 5, by choosing thesound or picture elements for the synchronization and broadcasting inphase advance of the element to be detected (more generally: of the pair10) and of the interactive service S to be executed when this element isdetected;

Step 2: when the moment of broadcasting the programme 15 has arrived, avideo server or a video recorder of the broadcaster 50 commences thebroadcasting of the audiovisual programme 15;

Step 3: broadcasting of the audiovisual programme 15 alone;

Step 4: the recognition unit 2 embedded in the terminal 70 then receivesthe audiovisual programme 15 pictures to which it has to synchronize theinteractive service S and analyses them;

Step 5: when the programmed picture and/or sound is detected, therecognition unit 2 notifies the interactivity engine 72 via theactivation unit 3, and the engine 72 can then trigger the execution ofthe interactive service S; in variants, the action to be triggered isthe displaying or the updating of the interactive service on theterminal 70;

Step 6: appearance of the interactive service S and of the audiovisualprogramme 15 simultaneously.

An advantage of this third embodiment as compared with the first two isthat a shift is avoided between the moment at which the audiovisualprogramme 15 is broadcast and the moment at which the interactiveservice S is inserted into the latter. However, it requires appreciableresources in the terminal 70 (CPU, memory, etc.).

In a variant embodiment, the specification unit 1 is designed tocommunicate beforehand to the recognition unit 2, several extractedportions associated respectively with one-to-one identifiers ofportions. Thus, during the phase of storing each extracted portion inthe storage space 20, the recording module 25 also stores thecorresponding portion identifier. During a subsequent step of specifyinga targeted detection, the specification unit 1 simply has to dispatchthe portion identifiers instead of the portions themselves, in therecognition elements 11 of the pairs 10. These identifiers then play therole of keys making it possible to link the appearance of the extractedportions and the other parameters, such as in particular timeout lags 13or 19 and/or actions to be triggered.

For example, the prior step of transmitting extracted portions definesthree identifiers ID1, ID2 and ID3 associated respectively with threeextracted portions POR1, POR2 and POR3 (Table 1), then the subsequenttransmission step giving instructions for synchronizing actions defineslags and actions A′ and A″ respectively associated with the identifiersID2 and ID1 (Table 2). TABLE 1 Recording of portions and of associatedidentifiers Portion identifier Extracted portion ID1 POR1 ID2 POR2 ID3POR3

TABLE 2 Instructions for synchronizing actions Portion identifier LagAction ID2 8 A′  ID1 10 A″

In a particular embodiment of this variant, the detection specificauonstargeted may also contain detection time slots. If the recognition unit2 detects that the current time is outside these time slots, it does notproceed to the analysis of the contents broadcast. In the converse case,the detection module is activated. Several recognition time slots maymoreover overlap. For example, the identifiers ID1 and ID2 arerespectively associated with a detection “Every Friday between 3 p.m.and 4 p.m.” and “Every day except weekends between 12 midday and 4p.m.”.

1-25. (canceled)
 26. Recognition unit for recognizing synchronization signals in at least one audiovisual programme received, said audiovisual programme comprising an audiovisual content intended to be broadcast to users and control information, said recognition unit comprising: a reception module and a recording module, for receiving and recording in a storage space, recognition elements making it possible to obtain at least one extracted portion of the content of said audiovisual programme), a reception module for receiving at least one transmitted stream carrying said audiovisual programme, a detection module for detecting said synchronization signals in said audiovisual programme received, by means of said recognition elements stored in said storage space, by recognition in the content of said audiovisual programme received, of said extracted portion, and a transmission module for transmitting action instructions in case of detection of said synchronization signals in said audiovisual programme), said instructions being designed so as to trigger at least one action,
 27. Recognition unit according to claim 26, wherein said reception and recording modules for receiving and recording said recognition elements are designed so as respectively to receive and record also at least one timeout lag and in that the timeout module is designed to use said lag.
 28. Recognition unit according to claim 26, wherein the modules for receiving and recoding recognition elements and the module for transitting action instructions are designed so as respectively to receive, record and transmit identifiers relating to said actions to be triggered.
 29. Recognition unit according to claim 26, wherein each of said portions of content consists of at least one of the following portions: an image, an image part, a sound and any combination of at least two of said portions.
 30. Recognition unit according to claim 26 wherein said recognition elements include at least one Boolean operator, said detection module being designed to detect at least two of said portions of content in conjunction with said boolean operator and the transmission module being designed to transmit said action instructions in case of such detection.
 31. Recognition unit according to claim 26, wherein said recognition elements include at least one time information item, said detection module being designed to detect said portions of content in conjunction with said time information item and the transmission module being designed to transmit said action instructions in case of such detection.
 32. Recognition unit according to claim 31, wherein said time information item comprises at least one information item chosen from among a date of detection and a detection time slot.
 33. Recognition unit according to claim 26, wherein said recognition elements include at least one channel reference, said detection module being designed to detect said portions of content in conjunction with said channel reference and the transmission module being designed to transmit said action instructions in the case of such deletion.
 34. Recognition unit according to claim 26, wherein the reception module for receiving the recognition elements is designed to directly receive said extracted portion from among said recognition elements and the recording module is designed to record said extracted portion in the storage space.
 35. Recognition unit according to claim 26, wherein the reception module for receiving the recognition elements is designed to receive from among said recognition elements, instructions for extracting said extracted portion in at least one stream of an audiovisual programme previously received by the stream reception module, and said recording module is designed to extract directly said portion of said stream according to said extraction instructions and to record said portion in the storage space.
 36. Recognition unit according to claim 26, wherein the reception module for receiving the recognition elements is designed to receive from among said recognition elements, at least one identifier of said extracted portion, and in that said detection module is capable of retrieving from the storage space said extracted portion previously recorded and associated with said identifier, so as to recognize in the content of said audiovisual programme received said extracted portion.
 37. Specification unit for specifying synchronization signals associated with at least one audiovisual programme, said audiovisual programme comprising an audiovisual content intended to be broadcast to users and control information, and said synchronization signals being intended to be detected in at least one transmitted stream carrying said audiovisual programme and thus to trigger at least one action, wherein said specification unit comprises a preparation module for preparing recognition elements making it possible to obtain at least one extracted portion of the content of said audiovisual programme, and a transmission module for transmitting said recognition elements independently of transmissions of said audiovisual programme, to at least one recognition unit intended to detect said synchronization signals in said transmitted stream carrying said audiovisual programme, by recognizing said extracted portion in the content of said audiovisual programme, and the preparation and transmission modules of said unit are designed respectively to prepare and transmit at least one action timeout lag in case of detection of said synchronization signals, said specification unit preferably being capable of cooperating with said recognition unit.
 38. Specification unit according to claim 37, wherein the preparation and transmission modules of said unit are designed respectively to prepare and transmit identifiers relating to said actions to be triggered in case of detection of said synchronization signals.
 39. Specification unit according to claim 38, wherein said action identifiers relate to at least one of the following actions: broadcasting of an interactive service, triggering of an interactive service, triggering of an update of an interactive service, triggering of a recording of said audiovisual programme and connection to a website.
 40. Assembly for activation by recognition of synchronization signals in at least one audiovisual programme received, said audiovisual programme comprising an audiovisual content intended to be broadcast to users and control information, the activation assembly comprising: a recognition unit for recognizing said synchronization signals in at least one transmitted stream carrying said audiovisual programme, by recognition of at least one extracted portion of the content of said audiovisual programme, by means of recognition elements making it possible to obtain said portion and recorded in a storage space, and an activation unit designed to trigger at least one action in case of detection of said synchronization signals by the recognition unit, wherein at least one of said recognition and activation units is designed to delay the triggering of said action by at least a determined timeout lag, in case of detection of said synchronization signals, said recognition unit preferably being.
 41. Activation assembly according to claim 40, wherein said activation assembly is designed to receive said timeout lag with said recognition elements.
 42. Synchronization system comprising: a specification unit for specifying synchronization signals associated with at least one audiovisual programme, said audiovisual programme comprising an audiovisual content intended to be broadcast to users and control information, a recognition unit for recognizing said synchronization signals in at least one transmitted stream carrying said audiovisual programme, by recognition of at least one extracted portion of the content of said audiovisual programme, in the audiovisual programme received, and an activation unit designed to trigger at least one action in case of detection of said synchronization signals by the recognition unit, the recognition unit and the activation unit forming an activation assembly, wherein the specification unit is designed to prepare and transmit to the recognition unit recognition elements making it possible to obtain said extracted portion, as well as at least one action timeout lag in case of detection of said synchronization signals, and in that the activation assembly is capable of delaying the triggering of said action according to said lag transmitted, in case of detection of said synchronization signals, the specification unit preferably being in accordance with claim 37 and the activation assembly.
 43. Broadcasting centre, wherein it comprises a device chosen from among at least a specification module in accordance with claim 37, a recognition module, an activation assembly, and a synchronization system.
 44. Services operator, wherein it comprises a device chosen from among at least a specification module in accordance with claim 37, a recognition module, an activation assembly, and a synchronization system.
 45. Terminal for receiving audiovisual programmes, wherein it comprises a device chosen from among at least a specification module in accordance with claim 37, a recognition module, an activation assembly, and a synchronization system.
 46. Method of activation by recognition of synchronization signals in at least one audiovisual programme received, said audiovisual programme comprising an audiovisual content intended to be broadcast to users and control information, said method comprising the following steps: reception of at least one transmitted stream carrying said audiovisual programme, detection of said synchronization signals in said audiovisual programme received by means of recognition elements making it possible to obtain at least one extracted portion of the content of said audiovisual programme and stored in a storage space, by recognition of said extracted portion, in the content of said audiovisual programme, and triggering of at least one action in case of detection of said synchronization signals in said audiovisual programme, wherein the triggering of said action is delayed by at least one determined lag in case of detection of said synchronization signals, said recognition method preferably being implemented by means of an activation assembly.
 47. Method of specifying synchronization signals associated with at least one audiovisual programme, said audiovisual programme comprising an audiovisual content intended to be broadcast to users and control information, said synchronization signals being intended to be detected in at least one transmitted stream carrying said audiovisual programme and thus to trigger at least one action, wherein said method of specification comprises the following steps: preparation of recognition elements making it possible to obtain at least one extracted portion of the content of said audiovisual programme, transmission of said information independently of transmissions of said audiovisual programme, for detection of said synchronization signals in said transmitted stream carrying said audiovisual programme, by recognition of said extracted portion in the content of said audiovisual programme, and transmission of at least one action timeout lag in case of detection of said synchronization signals independently of transmissions of said audiovisual programme, said specification method preferably being implemented by means of a specification unit.
 48. Synchronization method comprising the following steps: a step of specifying synchronization signals associated with at least one audiovisual programme, said audiovisual programme comprising an audiovisual content intended to be broadcast to users and control information, in which recognition elements making it possible to obtain at least one extracted portion of the content of said audiovisual programme are specified for said detection, a step of detecting said synchronization signals in at least one transmitted stream carrying said audiovisual programme, in which said synchronization signals are detected in said audiovisual programme received, by recognition of said extracted portion in the content of said audiovisual programme, and a step of triggering at least one action in case of detection of said synchronization signals, wherein the triggering of said action is delayed by at least one determined lag in case of detection of said synchronization signals, said synchronization method preferably being implemented by the synchronization system of claim
 17. 49. Method according to claim 46, wherein said audiovisual programmes comprise at least one recognition part containing at least one of said recognition portions, and at least one live transmission intended to be broadcast following said recognition part, in such a way that said synchronization signals are detected during the broadcast of said recognition part and that said action is triggered during the broadcast of said following live transmission, by means of said timeout lag.
 50. Method according to claim 47, wherein said audiovisual programmes comprise at least one recognition part containing at least one of said recognition portions, and at least one live transmission intended to be broadcast following said recognition part, in such a way that said synchronization signals are detected during the broadcast of said recognition part and that said action is triggered during the broadcast of said following live transmission, by means of said timeout lag.
 51. Method according to claim 48, wherein said audiovisual programmes comprise at least one recognition part containing at least one of said recognition portions, and at least one live transmission intended to be broadcast following said recognition part, in such a way that said synchronization signals are detected during the broadcast of said recognition part and that said action is triggered during the broadcast of said following live transmission, by means of said timeout lag.
 52. Computer programme product, wherein it comprises programme code instructions for executing the steps of one of the methods according to claim 46 when said programme is executed on a computer.
 53. Computer programme product, wherein it comprises programme code instructions for executing the steps of one of the methods according to claim 47 when said programme is executed on a computer.
 54. Computer programme product, wherein it comprises programme code instructions for executing the steps of one of the methods according to claim 48 when said programme is executed on a computer. 